Small watercraft often rely on a fin or a plurality of fins to provide horizontal lift or thrust to aid in tracking, steering, and stabilization of the watercraft. Some classes of fins also provide vertical lift to the watercraft.
A hydrofoil would be one example of a complex fin which provides vertical lift. Hydrofoils come in many shapes and designs but a common design for a hydrofoil intended for small watercraft comprises a keel attached to an optional longitudinal body and attached to at least one wing. Many different designs for hydrofoil wings and bodies exist but a keel is a commonality across many of these designs and is referred to as a hydrofoil keel.
Fins can be designed to be removable or non-removable from the watercraft.
Fins attached by a non-removable means cannot be interchanged between watercraft and the fin cannot be easily removed to aid in storage and transport of the watercraft. If damaged, non-removable fins can be expensive to repair since they are incorporated into the watercraft. Non-removable attachment could include attachment by molding or gluing the parts together.
Removable fins are common in watercraft such as surfboards and kiteboards, but these removable fins generally require the watercraft to be designed to incorporate the fin by means of a non-removable fin receptacle. Non-removable fin receptacles such as fin boxes, bolt holes, threaded holes, cavities, recesses, slots and the like are generally designed into the watercraft. These non-removable fin receptacles can limit the placement of fins on the watercraft and can limit the types of fins that are used.
It is common for water enthusiasts to own multiple watercraft. Users have long desired for there to be an easy method and apparatus to attach a removable fin to a watercraft and swap that same fin between watercraft even if the watercraft was not originally designed with the matching fin receptacle. For example, a surfer who already owns a surfboard without a hydrofoil keel receptacle cannot easily or non-destructively attach a hydrofoil keel to their existing surfboard. Likewise an inflatable standup paddle board owner cannot easily add a removable fin to their inflatable, board if′ the fin receptacle was not designed into the original board.
There are essentially four “groups” of related art that should be discussed in detail.
Group one depicts removable fins which rely on non-removable fin receptacles. Related art U.S. Pat. No. 8,246,406 to John Field depicts such an assembly. John Field's removable fin mates with a non-removable fin receptacle described as a “fin box”. Typically these fin boxes are incorporated into the watercraft and the fin box is not easily removable or easily adjustable. Also in this group is related art U.S. Pat. No. 7,108,571 B2 to Dean Geraghty. Dean Geraghty depicts a removable fin box which fits inside a recess or cavity on the watercraft. While Dean Geraghty's fin box is removable it shares similar limitations to non-removable fin boxes due to the use of a recess which is incorporated into the watercraft. The recess or cavity is effectively a non-removable receptacle. The location of the recess or cavity is not easily adjusted after the watercraft is manufactured.
Group two depicts fin box adapters. In this group, adapters are designed to allow removable fins to be used in more than one style of non-removable fin receptacles. Related art U.S. Pat. No. 5,176,553 to Lawrence Tuttle depicts such an assembly. Lawrence Tuttle's assembly allows a fin designed for a narrow and shallow fin receptacle to be used on a watercraft that has a wider and deeper fin receptacle. While Tuttle's assembly allows for a removable fin to be used on watercraft with different fin receptacles, it requires the watercraft to have a non-removable receptacle to mate with the receptacle. Similar to group one, the non-removable receptacle is incorporated into the watercraft.
Group three depicts adjustable fins. Related art U.S. Pat. No. 4,421,492 to Donn Leva depicts such an assembly. Donn Leva describes a non-removable fin receptacle which is essentially a slot incorporated into the watercraft. The fin attaches to the slot which allows the fin to slide forwards and backwards. While this slot allows for more adjustment than a standard fin box, the watercraft still incorporates a non-removable fin receptacle in the form of a slot which suffers from many of the same drawbacks described previously.
Group four depicts breakaway fins. Related U.S. Pat. No. 4,701,144 to Glen DeWitt depicts such an assembly. Glen Dewitt's fin incorporates a breakaway tab that allows the tin to separate from the watercraft in the event excessive force is exerted. This assembly incorporates a non-removable fin receptacle which suffers from many of the limitations of group one. Additionally, in this specific example, the retaining tab has to be replaced when the fin separates so the fin does not separate non-destructively.